Microprocessor designers have increasingly endeavored to improve performance in various microprocessors by increasing clock speeds and adding parallelism. Large blocks of random access memory (RAM) are included within the microprocessor for data storage and for program storage in order to reduce memory access times. Various types of input/output devices are included within a microprocessor integrated circuit in order to reduce total system chip count and cost. Serial ports are an example of a class of input/output devices that are commonly included with microprocessors. Various examples of serial ports may be found on digital signal processors available from Texas Instruments Incorporated, including TMS320C2x and TMS320C5x series of devices. Various features are included within the serial ports on these devices, such as Full-Duplex communication, double buffered data registers which allow a continuous data stream, independent framing and clocking for receive and transmit, direct interface to industry standard Codecs, Analog Interface Chips (AICs), and other serially connected A/D and D/A devices, and external shift clock generation or an internal programmable frequency shift clock.
An object of the present invention is to provide improvements in the operation and control of serial interfaces for microprocessor integrated circuits.